Welcome aboard! Fishing from a boat I would try a bead head or weighted nymph fished on an indicator. Start fishing your fly a few feet down and keep moving the Indy up to get a little deeper until you find fish.

You may also want to try a weighted streamer or wooly bugger (white is a good minnow imitation). Cast out and count down to allow it to sink and strip it back slowly.

Be careful casting in a boat though, pinching down the barbs on your fly would be much appreciated by the fish...and your fishing partner.

Although a beadhead is a good choice i think. I'd use a clouser minnow , using basically the same countdown method AFish said , after you reach the depth retreive it with a slow , Slow , short strip. And if there are fish rising my goodness use a dry fly , try to see what they are eating and match it as close as you can with one of your flies , when trout are feeding on top in lakes they like to "cruise" around without using up much energy , like coasting slow on a bike , try to time your cast to the place you think the trout will coast to next. You might have to watch them awhile but that's cool too. If they are chasing flies that are moving around on top , do the same thing with your fly , skitter/skate/move it. HOPE YOU NAIL 'EM